Enterprise Edition transit routers support custom route tables, which let you isolate routing domains and control traffic forwarding between network instances. After creating a custom route table, associate it with network instance connections to define how the transit router forwards traffic. Add custom routes and attach prefix lists to further control routing behavior.
What you can do:
Background
Every transit router has a system route table, created automatically when the transit router is created. Enterprise Edition transit routers additionally support custom route tables; Basic Edition transit routers do not. For information on transit router editions, see View the edition of a transit router.
The following table summarizes the differences between the two route table types:
| Route table type | Created by | Isolated from other tables | Deletable |
|---|---|---|---|
| System route table | System (automatically, on transit router creation) | Yes | No |
| Custom route table | You (manually) | Yes — similar to virtual routing and forwarding (VRF) on traditional routers | Yes |
After you connect a network instance to a transit router, configure associated forwarding to associate that connection with a custom route table. The transit router then forwards traffic from the network instance by querying the associated route table. Add custom routes and attach prefix lists to further refine routing behavior.
Create a custom route table
Log on to the CEN console.
On the Instances page, click the ID of the CEN instance.
Go to Basic Information > Transit Router and click the ID of the transit router.
Click the Route Table tab.
In the left-side section, click Create Route Table.
In the Create Route Table dialog box, configure the following parameters and click OK.
Parameter Description Transit Router Select the transit router. The transit router ID is displayed automatically. Route Table Name Enter a name for the route table. Description Enter a description. Tag Add one or more tags to the route table. Each tag consists of a key and an optional value.
- Tag Key: Up to 64 characters. Cannot be an empty string, start withacs:oraliyun, or containhttp://orhttps://.
- Tag Value: Up to 128 characters. Can be an empty string. Cannot start withacs:oraliyun, or containhttp://orhttps://.
For more information, see Manage tags.Multi-region ECMP Routing Enable to treat routes learned from virtual border routers (VBRs) in different regions as equal-cost multipath (ECMP) routes when all route attributes except region ID are identical. Disabled by default.
When disabled, the transit router forwards traffic based on region IDs in alphabetical order if routes share the same attributes. When enabled, such routes are treated as equal-cost and traffic is distributed across them.
To enable multi-region ECMP routing, turn on Multi-region ECMP Routing, read the information in the message that appears, and then click OK.
For details, see Multi-region ECMP routing for VBRs in different regions.
API: CreateTransitRouterRouteTable — creates a custom route table for an Enterprise Edition transit router.
View route tables of an Enterprise Edition transit router
Log on to the CEN console.
On the Instances page, click the ID of the CEN instance.
Go to Basic Information > Transit Router and click the ID of the transit router.
Click the Route Table tab.
In the left-side section, click the route table ID.
On the route table details page, view the following information:
Information Reference Routes View routes of an Enterprise Edition transit router Associated forwarding correlations Associated forwarding Route learning correlations Route learning Routing policies Routing policy overview Routes generated from a prefix list Prefix lists Aggregate routes Aggregate routes
API: ListTransitRouterRouteTables — queries the route tables of an Enterprise Edition transit router.
View the route table of a Basic Edition transit router
Basic Edition transit routers have a single system route table and do not support custom route tables.
Log on to the CEN console.
On the Instances page, click the ID of the CEN instance.
Go to Basic Information > Transit Router and click the ID of the transit router.
Click the Route Table tab to view:
Information Reference Routes View routes of a Basic Edition transit router Routing policies Routing policy overview
Delete a custom route table
The system route table cannot be deleted. Before deleting a custom route table, remove all associations and routes listed below.
Associations and policies (the route table must not be linked to any of the following):
Associated forwarding correlations — see Delete an associated forwarding correlation
Route learning policies — see Delete a route learning policy
Prefix list associations — see Disassociate a prefix list from a transit router route table
Routes (the route table must not contain any of the following):
Custom routes — see Delete a custom route from a route table of an Enterprise Edition transit router
Aggregate routes — see Delete an aggregated route
To delete the route table:
Log on to the CEN console.
On the Instances page, click the ID of the CEN instance.
Go to Basic Information > Transit Router and click the ID of the transit router.
Click the Route Table tab.
In the left-side section, click the route table ID.
In the Route Table Details section, click Delete.
In the Delete Route Table message, click OK.
API: DeleteTransitRouterRouteTable — deletes a custom route table from an Enterprise Edition transit router.
API reference
| API | Description |
|---|---|
| CreateTransitRouterRouteTable | Creates a custom route table for an Enterprise Edition transit router |
| UpdateTransitRouterRouteTable | Modifies the name and description of an Enterprise Edition transit router route table |
| ListTransitRouterRouteTables | Queries the route tables of an Enterprise Edition transit router |
| DeleteTransitRouterRouteTable | Deletes a custom route table from an Enterprise Edition transit router |